Immunological assay reagents making use of an antigen-antibody reaction are used as a reagent for quantitatively analyzing a particular component, such as an antigen or antibody to be assayed, in a liquid sample. Of the reagents, an immunological latex turbidimetry method is widely used, because a quantitative determination can be carried out by an automated analyzer and easy procedures. In the immunological latex turbidimetry method, an agglutination of the latex particles is analyzed by a change of an absorbance or a turbidity. The agglutination is caused by an antigen-antibody reaction between the latex particles carrying thereon antigens or antibodies, and antibodies or antigens in a liquid sample.
Recently, a simple, quick and high-sensitivity analysis has been desired in an analyzing field using an automated analyzer as above. Thus, an immunological latex turbidimetry method and a reagent therefor have been required to meet the above need.
Up to now, the immunological latex turbidimetry reagent contains a bovine serum albumin (hereinafter sometimes referred to as BSA) and/or a thermally modified BSA, to enhance a sensitivity, accelerate a dispersion of suspended latex particles, or avoid a non-specific agglutination caused by a non-specific binding of proteins or the like in a sample, to the latex. This is because some patients from which samples are taken have antibodies to BSA, due to a recent change of eating habits. The BSA added to an analyzing reagent can take up an anti-BSA antibody of the patient. For example, in an immunological latex turbidimetry reagent carrying an antigen stemmed from a streptococcus haemolyticus component (streptolysin O; hereinafter sometimes referred to as SLO) for detecting an SLO antibody, a thermally modified BSA is added for absorbing the non-specific reaction. However, there still remain samples showing a non-specific reaction which cannot be absorbed only by an addition of the thermally modified BSA. This has been a problem to be solved.